Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. The hydrocarbon fluids produced from the well can be transported to other locations via a pipeline that is buried in the ground and which extends over a very long distance. Reliably obtaining information about the integrity of the pipeline, as well as information about other structures that extend over long distances, can be difficult.
One manner in which information can be obtained about the condition of a structure is to use a distributed fiber optic sensing system, such as a distributed temperature sensing (DTS) system or a distributed vibration sensor (DVS) (also referred to as a distributed acoustic sensor (DAS)) system. Fiber optic sensors employ the fact that environmental effects, such as pressure, strain, vibration, and temperature, can alter the amplitude, phase, frequency, spectral content, or polarization of light propagated through an optical fiber. Advantages of fiber optic sensors include their light weight, small size, passive nature, energy efficiency, and ruggedness. In addition, fiber optic sensors have the potential for very high sensitivity, and wide bandwidth. In general, measurements are made using fiber optic sensors by detecting returned light that is scattered by naturally-occurring reflective features in the fiber in response to a probe signal, and can be based on spontaneous Raman scattering, stimulated Brillouin scattering, or Rayleigh scattering. When a distributed fiber optic sensor is used with an appropriate measuring system to interrogate and acquire information from the sensor, selected environmental parameters can be monitored at multiple locations at the same time.